In the usually used encapsulating method for a substrate-based electronic device, during removal, the encapsulant sticks on the runner and the gate on the substrate, substrate and package are often damaged. In severe cases, damage reaches even to the encapsulated electronic device, resulting in reduction in the pass rate of encapsulating. FIGS. 1 and 2 show the relative location of encapsulating mold, encapsulant, and substrate-based electronic device in conventional encapsulating method, wherein FIG. 1 is a vertical cross sectional view, and FIG. 2 is a cross sectional sketch along the A--A direction in FIG. 1. In the figures, number 100 is an encapsulating mold, 110, 120, 130, 140 and 150 are its upper mold, lower mold, a cavity, a pot and a runner, respectively, 131 is a transfer ram on up side of the pot; 200 is an encapsulant; 300 is a substrate-based electronic device; 310 and 320 are its gate and substrate, respectively. When the encapsulant 200 in the pot 140 is liquidized, then filled in the cavity 130 through the runner 150/the gate 310, and directly covers on the substrate 320, said substrate 320, package and/or electronic device are often damaged during degating.
It is the constant effort of the mold/encapsulating maker to resolve the above defect of ordinary encapsulating method. The U.S. Pat. No. 5,635,671 offers one solution, which consists of pre-designing a degating region on the substrate. The degating region is plated with metal (gold or palladium)layer, so that adhesion force between encapsulant and degating region becomes far smaller than that between encapsulant and substrate to overcome the defect of ordinary encapsulating method, that is the substrate, the package and/or the electronic device are damaged during degating the runner and the gate on the substrate. Nevertheless, the gold or palladium plating process in this method will raise the cost of the substrate, and also add a requirement for one more quality control/guarantee step. Furthermore, in degating step of said manufacturing processes, because of the use of the high sticky encapsulant produces a phenomenon of peeling gold plating layer occurs. This is equal to the defect of the ordinary encapsulating method can not be completely removed by this method. Besides, U.S. Pat. No. 5,635,671 has another quality problem as follows. FIG. 3 is a drawing of its substrate-based electronic device, and FIG. 4 shows the relative position of its encapsulating mold/substrate-based electronic device along the direction the B--B in FIG. 3, in which definitions of 110, 150, 310, 320 and 330 are the same as before, 321 is solder resist on the substrate 320, 321a and 321b are solder resists 321 on edge area of the degating region respectively, 331, 332 and 333 are gold plating layer and copper plating layer on the degating region 330 and base material (such as bismaleimide trisazine resin) on the degating region 330, respectively. As coefficients of thermal expansion of copper/gold layer and B.T. resin are different, after the encapsulant is solidified, temperature decreases (from liquefaction temperature, e.g. 175.degree. C. down to room temperature) can produce warpage of the substrate, which will introduce unsatisfactory coplanarity of solder ball, after successive process of solder ball placement. This will then result in the quality problem on bad contact of SMT. Besides, in injecting encapsulant, the phenomenon that molded flash may remain on the gold plating layer of a product after press molding due to the smaller width of the runner/gate than that of the plating degating region. This will effect quality of the product. As edge areas 321a and 321b of solder resist and encapsulant of the runner are close together, breakdown of solder resist edge areas 321a and 321b may happen, during degate process. This also will effect quality and reliability of the product.